Platelet aggregation is induced in cerebral microvessels of living mice. The response can be quantified and will be compared in four groups of mice: those with alloxan induced diabetes, those with streptozotocin induced diabetes, those with genetic diabetes, and normal controls. Insulin and a variety of drugs believed to alter vascular injury and/or platelet aggregability will be used in an effort to ameliorate abnormalities that may be detected. Blood glucose and insulin levels will be monitored in order to see whether a correlation exists between values of these parameters and any detected abnormalities in the propensity of platelets to aggregate in vivo.